Having lapped under the race lap record in Friday practice at Mugello, Jorge Lorenzo rose to new heights by officially smashing the all-time best lap in Saturday morning's final practice session for the Italian MotoGP.

With threatening dark clouds on the horizon, Yamaha's 2012 title leader broke the 1m 48.076s, set by Casey Stoner in qualifying last year, on only his third lap of the morning, using the hard rear tyre.

Lorenzo then pounded out a series of further improvements, lowering his best time to a 1m 47.584s by his sixth of 19 laps, which kept him on top to the chequered flag. Once again, Lorenzo was consistently quick throughout, with most of his laps under 1m 48s.

But he was pursued closely, with Casey Stoner getting within 0.289s on his fourth of 16 laps, before Repsol Honda team-mate Dani Pedrosa slotted in between the world champions with a lap just 0.095s from Lorenzo on his 18th and final circulation.

Lorenzo holds a 14-point lead over Pedrosa and 20-point advantage over Stoner heading into this weekend.

Lorenzo's team-mate Ben Spies made late gains for fourth place, just 0.302s from the top, with Andrea Dovizioso pushed down to fifth (+0.444s) but remaining the top satellite and Italian rider.

Yamaha Tech 3 team-mate Cal Crutchlow, Ducati's Nicky Hayden, Pramac's Hector Barbera, Honda LCR's Stefan Bradl and Ducati's Valentino Rossi completed the top ten.

Rossi - as traditional - debuted a new helmet on Saturday morning at his home event. The helmet features an Italian singer and the quote "Let's stick together". The message would appear good news for those hoping Rossi stays with Ducati for 2013.

Alvaro Bautista will go into qualifying after falling in all three free practice sessions, the San Carlo Honda Gresini rider being kicked-off at considerable speed after losing the front end of his RC213V as he touched a kerb on corner entry this morning.

Bautista set the eleventh quickest time, with Aleix Espargaro the top CRT rider in twelfth.

Mugello boasts the highest top speeds of the season, with the official MotoGP record of 349.3km/h (217.04mph) set at the circuit by Pedrosa in 2009.

Barbera clocked 346.7km/h on Friday, while Rossi's onboard camera graphics registered 351km/h this morning.

However, the Italian's official post-session data listed his FP3 top speed as 'only' 339.8km/h - perhaps due to the location of the official speed trap - meaning the record remains.

Barbera was again officially quickest this morning at 342.7km/h.

Qualifying takes place this afternoon.

Saturday practice:

1. Jorge Lorenzo
2. Dani Pedrosa
3. Casey Stoner
4. Ben Spies
5. Andrea Dovizioso
6. Cal Crutchlow
7. Nicky Hayden
8. Hector Barbera
9. Stefan Bradl
10. Valentino Rossi
11. Aleix Espargaro
12. Alvaro Bautista
13. Randy De Puniet
14. Ivan Silva
15. Michele Pirro
16. Danilo Petrucci
17. Yonny Hernandez
18. Mattia Pasini
19. James Ellison
20. Colin Edwards